Nonjamming stop for linear actuators



'ov. O, 1953 J. E. CHAPMAN EI'AL NONJAMMING STOP FOR LINEAR Filed June 5, 1949 ACTUATORS JRMES E- Cf/fiPM/QN LLOVO D- BEI HN INVENTOR5 ATTORNEY Patented Nov. 10, 1953 NONJAMMING STOP FOR LINEAR ACTUATORS James E. Chapman, Los Angeles,

Calif., assignors Los Angeles, Calif., a corpo- Bevan, Van Nuys, rett Corporation, ration of California and Lloyd D. to The Gar- Application June 3, 1949, Serial No. 97,054 12 Claims. (Cl. Id-424.8)

This invention pertains to extensible struts, and relates particularly to a means for reducing or eliminating a jam which may occur at either of the extreme limits of movement of such a strut.

Extensible struts of the electrically actuated type are extensively used in aircraft, for example, for the remote control of movable airfoil surfaces. In some applications of such linear actuators it has been found that binding or galling of the translatory member with respect to the stationary member occurs at either or both of the fully retracted and extended positions. As a consequence of such a jam, it is not unusual that the motor upon reversal is incapable of both reducing the jam and accelerating the load. The condition is aggravated by virtue of the fact that such a binding or galling jam occurs at surfaces which move relative to each other in both rotary and longitudinal movements. Hence when the members of the strut are extended or retracted to an extreme limit of movement a quantity of kinetic energy is dissipated as heat because of the jam at the surfaces of the moving parts.

It is an object of this invention to provide means for converting at least a part of the kinetic energy of a jam into potential energy available to assist in unjamming the parts. It is a further object to provide a novel stress member associated with one of the jamming members, wherein the greater portion of the jam kinetic energy is converted to and stored as the potential energy of a stress induced in the member in the form of torsional and/ or longitudinal stress, the latter stress being either compressional or tensional.

Further objects will be apparent upon consideration of the preferred embodiment of the invention shown on the drawing and described in detail herein. Since many changes could be made in the preferred embodiment without departing from the scope of the invention, it is intended that all matter contained in the description and shown in the accompanying drawing shall be interpreted as being illustrative rather than as being restrictive of the scope of the invention.

The single figure of the drawing is a partially sectioned view of an extensible strut of the electrically actuated type.

The strut, generally indicated at H], is adapted for pivotal mounting to members (not shown) for inducing relative movement therebetween by means of eye fittings II and H, which are prevented from rotation about the axis of the strut by virtue of their attachment to the aforementl-oned movable members. Fitting II is secured by means of screws Ila to a. gear housing I3, within which a train of gears is disposed for transmitting power from an electric or other type of motor M to the relatively movable primary parts of the strut to be described. As shown, the gear train comprises a spur gear l5 driven by the pinion shaft it of motor I4, and a spur gear ll driven by the pinion portion I8 of a countershaft i9 to which the gear I5 is secured, as by splining engagement therewith and by a pin 20. The countershaft I9 is rotatably contained within the housing l3 by means of anti-friction bearings 2| and 22.

The spur gear I! is secured by means of a pin 23 to the reduced portion 24 of a jack screw shaft 25 which comprises Ol'lGDf the two relatively movable primary parts of the strut aforementioned. Anti-friction bearings 26 and 21 support the jackscrew shaft 25 for rotation within the housing l3 on either side of the spur gear I1. Between the gear l1 and bearing 21 a pinion gear 28 is secured to the shaft 25 and adapted to engage a gear 29 which may actuate an elec tric switching mechanism in the control box 30, the latter forming no part of the invention and hence not being described herein. Distal of the bearing 21 the shaft 25 is threaded to receive a cooperating nut 3| for translational movement thereof when the shaft is rotated, the nut 3| constituting the second of the aforementioned relatively movable primary parts of the strut. A thrust sleeve 32, to the outer end of which the eye fitting I2 is secured, is attached at its inner end to the nut 3| by any preferred means, such as dimpling or brazing. Secured to the housing l3, and overlying the thrust sleeve 32 is a dust tube 33 within which the sleeve 32 is adapted to move axially.

Attached to the end of nut 3| in any convenient manner is a stress collar 34, preferably of steel, whose purpose will be hereinafter described. A stress washer 35, likewise preferably fabricated of steel, may be brazed or otherwise affixed to the inner end of fitting I2 if desired.

The iackscrew shaft 25 has an axial bore 250: throughout its length and has therewithin a stress rod member 36, of a slightly smaller diameter than the shaft bore, and anchored therewithin at its leftward end by suitable means, such as brazing. An enlarged head 31 on the rightward end of the member 35 is of slightly smaller diameter than the inside diameter of the thrust sleeve 32, whereby it is adapted to contact the stress collar 34 when the strut is in extended position and to contact the stress washer 36 when the strut is retracted.

It is now apparent that extension of the strut to its extreme limit causes the nut 3| to traverse the threads of 'shbift 25 untll'the collar '34 contacts the enlarged portion 31-01 "the-member 36, at which time a tendency towards further strut extension will result in (a) tension stress in member 36 by virtue of the linear rnotion of the nut 3| with respect to shaft zraua 'ibfforsin stress in member 36 by virtue of rotary motion of the shaft 25 (and thus of the mmber iwaifd its enlarged head 31) Withresbect to-mHt' W.

Likewise it is apparent 'th atrtraftibn'bf the strut to its other extreme limit causes the nut 3| to traverse the threads of shaft 25 until the washer 35 contacts the opposite face of the enlarged head 31 of the member 36, at which time a tendency toward further strut retraction will J'BsIIIt'in (a) compressionstress, and '(b) torsion stress; in member 36.

In either event, the mbving'parts-come'to rest -in non-jam association; since the kinetic eriergy 'of the-usual jam isnoW stored as potential energy in-the resilience of the stress rodmembcnfifl and -isempidyed to augment thestarting'torque'ap- *plied by E the motor-when reverse movement is to beefiected.

We'claim:

1; A non-slamming "stop for members movable rbtatively and translationally of eachother to 'one limit of movement "thereof, comprising: 'a first stress-=member *securedtoone of said movable members; a second other of-said-movable members friction surfaces on said stress members, at least one of -saidstress members being'aclapted to convert atleast aiportion of the kinetic energy of-ajam to'the poten- "tial energy of alongitudinaband torsional stress in one of said stress members upon' frictional engagement of said'surfacesrand means for'im- 'parting rotative-movement to one of -said'mov- 'able members.

-2. The inventionofelaim 1 further characterized in that the potential energy-stering-stress member is secured to the rotative one of said =movable members.

3. -A non-jamming stop for-members -movable rotatively and 'translationally of each'other-between limits of movement thereof, first stress 'member secured to one ofsaidqnovable members; a second stress member secured to the =other one of said movable members; a third stress member likewise secured to the said other one of said-movablemembers;friction surfaces on said stress members, said second and third stress members being secured'in-sueh-znan- -ner that said second stress mt-imber frictionally engages said first stress member by means ofsaid friction surfaces adjacent one limit of movement of said movable'members, and-said third-stress member frictionally engages said first stress member by 'meansof'said friction siu'facesarljacent'the-other'limit' of movement of said movable members'whereby' at least one of said stress "m'mbersconverts at least a portion of 'the kinetic "energy of a j'am' to the potential energy of a longitiidinal'and torsional stress in one of said stress upon frictional engagement; and means for-ithparting'rotative movementto one of said 'movable'mmbers.

4. The invention of claim 3 further character- Tzedin that 'said'fi'rststress member is the Dote'nti'al energy storing member.

stress member =securedto the comprising a said movable members for imparting rotative movemenetneretb:

a first stress member secured 'tobfiebftfldmbVable members; a second stress member secured"to the other of said movable limbers; and friction surfaces on said stress members, at least one of said stress members beir'ig adapted to convert at least a portion of the kinetic energy of a jam to the potential energy of 'alongitudinal and a torsional stress dn one of -said stress members upon frictional eng agemerit of said surfaces.

7. The invention'of 'eiaim'fi further characterized in that the potential energy storing stress member is secured to the rotative oneofsaid movable members.

8. An extensibie s-trutfor the movement'of one part relative to another part -between limits of movement thereof; comprising a. heusingfimeans connecting said housing with one ofsaid-parts; a first movabie member in saidhousing asecond movable member in threaded screw relatibnto said first movable "member; means connecting said second movable member with the other of said parts; means associated with' one of said movable members for imparting rotativeihovement thereto; a'fli'st stress mem'ber secured "to one *of said movable members; a second* stress member-secured to the other one of" said movable members; a third stress member" likewise secured tos'aid'oth'er one of 'said movabie members and friction surfaces on 'saidstress members, said second and third stress membersbeihg "secured in such manner that said second stress member fri'etionally *engages sald' first 'stres's member by 'means of said friction 'surrarces' at one-limit 'of movement of sa id' lhdvable' ihfiibers, efi'd said third stress lnen'iber 'fribtionally engages said'fiist st'ress member by means ofsaid frictlon 'surfaees at the other limitbi' movement ofsaid'mbvable members whereby at least one of said stressmembers convertsat least ap'o'rtion ofthe kinetic energy of ajam to the potential energy of'a'longitudinal and'torsional stress in said one-of said stress members uponfriotional engagement of said: surfaces.

9. The invention ofciaim 8 1 further characterized-in-that said first stressmember is the potential energy storing member.

10. The invention of claim *il 'further characte zed in that said first stress member isseoul'ed to the rotative oneof'saidmovable members.

11. An' actuator beinbrisinglnembtfis movable relative to "each other' -to-a limit ovmovemem, a torsion stress member connected witho'ne of said 1 nilnbers and" having a surface flibtionally engaging a terrace an the bther ofs'aiiiirlenibrs limit of movement, said engagement of "said surfaces at said limit of movement.

12. A gearing con":ririslrlg s'lr'irew be'rs movable I h and nutmemrel'altive to one anbtlier, said 'members having portions limiting said relative movement, one of said portions comprising a torsion stress means having a friction surface, the other of said portions also including a friction surface arranged to slidably engage the first friction surface at the limit of movement of the nut member relative to the screw member, said stress means becoming stressed after said surfaces are engaged.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date Fitz Gerald Dec. 5, 1939 Chapman Sept. 10, 1946 Werner Nov. 5, 1946 Jackson June 24, 1947 Werner Sept, 20, 1949 Hoover Mar. 25, 1952 

